50% of your EV energy consumption comes from wheels and tires

[Isaac Zachary]

My take on it is this:

1. You have a twisting force that causes the side walls to flex.
2. At the same time you have more downforce due to inertial forces caused by acceleration, which makes the tires squat.
3. Does this really reduce the radius and thus increase torque? Of this I'm not certain, as with every turn of the wheel the outer circumfrence of the tire does not change and therefore you get generally the same distance per turn with or without the sidewall flex.
4. We are dealing with flexible structures here (tires) and trying to apply the math that applies to solid ones (force x radius). But maybe it's more like a pulley (small diameter wheel pulling on larger diameter wheel).

[freebeard]

My take on it is this:

Trivial when compared with the downforce from the zoomie headers.

[j-c-c]

Originally Posted by freebeard

My take on it is this:

Trivial when compared with the downforce from the zoomie headers.

Consider this from years back, not sure if the efficiency balance has changed, but it used to be thought a Top Fueler was approx 33% efficient in converting to mechanical energy, another 1/3 was lost as waste heat, and 1/3 became acoustic energy. In a 6000hp motor, that means 6000 hp of acoustic energy, and if 1 hp equals 754? acoustic watts, that's approx 4,524,000 watts, and the most efficient large speakers are at best 33% efficient, most today are far below that. it would take 13,572,000 RMS watts to equal one Top fueler at full throttle.
This all circles back to any acoustic wind noise in your car while driving is wasted energy.

[j-c-c]

Originally Posted by Isaac Zachary

My take on it is this:

1. You have a twisting force that causes the side walls to flex.
2. At the same time you have more downforce due to inertial forces caused by acceleration, which makes the tires squat.
3. Does this really reduce the radius and thus increase torque? Of this I'm not certain, as with every turn of the wheel the outer circumfrence of the tire does not change and therefore you get generally the same distance per turn with or without the sidewall flex.
4. We are dealing with flexible structures here (tires) and trying to apply the math that applies to solid ones (force x radius). But maybe it's more like a pulley (small diameter wheel pulling on larger diameter wheel).

on #2, the only dim I see pertinent is the rolling radius, the free tread radius not in contact with the ground has only aero effects and maybe some inertia effects as it recontacts the ground, and maybe as some stored energy being at a larger radius traveling at a faster rotational speed?

[freebeard]

Imagine if those zoomie pipes each had a bypass nozzle to increase the air flow 50%?

-- At the same time you have more downforce due to inertial forces caused by acceleration, which makes the tires squat.

The entire weight of the vehicle is trying to climb the ring gear. Meanwhile back at the contact patch:

[IMG][/IMG]

[Hersbird]

https://www.caranddriver.com/feature...res-explainer/

So it shrinks by 6 inches, then grows by 2. So yes that changes the gear ratio but think about it, it also slowly is lifting the car 8 inches right when it needs traction the most. For every action there is an equal and opposite reaction. If I step on a scale with my body squatted 6 inches I will still weigh 200 pounds, but as I stand up fully the scale will register more than 200 pounds.

This is just the tire contraction and expansion, I believe there is also more of the same in the suspension design.

Anyway, getting over 4 Gs of acceleration without any meaningful speed yet from aerodynamic downforce, comes from other sources.

[j-c-c]

You omitted while you were in the act of squatting, the scale would also register less than 200lbs, and BTW, your mass never changed.

[Hersbird]

Originally Posted by j-c-c

You omitted while you were in the act of squatting, the scale would also register less than 200lbs, and BTW, your mass never changed.

But the car isn't actually moving forward yet at that point. It squats and stores that energy while the front tires are still stationary.
In pro level drag racing you get a .400 sec delay from when the yellow lights go to when the green (or red) light goes (.500 secs for amateur) So the car "starts" before it actually leaves the beam which is on the front wheel. Many tracks have now adjust the system so it shows .000 being a perfect reaction time but it's actually just using the .5 or .4 sec delay and subtracting it out. I guess it was too confusing to call a .400 or .500 reaction time perfect even though if it were any faster it would mean a red light disqualification.

Then there is the whole matter of rollout where technically the whole car can travel a foot before the tire clears the starting beam and a red or green light is determined.

[j-c-c]

Originally Posted by Hersbird

But the car isn't actually moving forward yet at that point. It squats and stores that energy while the front tires are still stationary.

Not sure I completely agree with that. Are we focusing on the body squatting or the tire compressing?
The tire squat is significantly from weight transfer and the windup observed in the wrinkling/compression of the sidewall, both require movement in order to occur, and the rotation of the driven rear tire satisfies for me that "movement", regardless of when the front tire moves.

Not sure how the .400 light or rollout are pertinent here.

It should also be noted the body when seen rising due to suspension design under acceleration is pushing against tire adding tire load and compressing the tire further. The sidewall reaction/height is a useful indicator of this result.

[freebeard]

I like 60-foot times [as a metric] because that's about the width of an intersection.